1. Field of the Invention
The present invention relates to a hard disk drive, and more particularly, to a hard disk drive having a vibration-reducing damper between a spindle motor and a cover plate.
2. Description of the Related Art
A hard disk drive is one of the auxiliary memory systems of a computer, and is intended to read stored data from a stack of magnetic disks, or to write data to the magnetic disks with magnetic heads. Recently, various research and development have been performed in order to realize higher speed, more increased storage capacity, and more reduced vibrations and noises of such a hard disk drive.
FIG. 1 is an exploded perspective view schematically illustrating a conventional hard disk drive, and FIG. 2 is a vertical section view illustrating an assembly structure of a housing and a spindle motor of the hard disk drive shown in FIG. 1.
Referring to FIG. 1, a hard-disk drive is provided with a housing 10, a spindle motor 30 installed in the housing 10 for rotating magnetic disk unit (hard disk unit) 20, and a head assembly 40 for reading data from the magnetic disk unit 20 or writing data to the magnetic disk unit 20.
The housing 10 is installed in a main body of a computer, and comprises a base plate 11 for supporting the spindle motor 30 and the head stack assembly 40, and a cover plate 12 which is joined to the upper part of the base plate 11 for enveloping and protecting the magnetic disk unit 20 and the like. The housing 10 is usually made of a stainless steel or aluminum alloy material.
The magnetic disk unit 20, a recording medium for writing data thereto, has one or a plurality of magnetic disks spaced a predetermined distance from each other, and is installed to be rotated by the spindle motor 30.
Now, an assembly structure of the housing 10, the spindle motor 30, and the magnetic disk unit 20 will be described in detail with reference to FIG. 2.
The spindle motor 30 is supported by a flange 31 which is fixedly installed on the base plate 11. The lower end portion of a shaft 32 of the spindle motor 30 is fixed to the flange 31, and the upper end portion thereof is directly fixed to the cover plate 12 by a screw 39. To this end, a through hole 13 is formed at the cover plate 12 so that the threaded portion of the screw can pass through the through hole 13. A hub 33 is installed on the outer circumference of the shaft 32 with bearings interposed therebetween so that the hub 33 can rotate. The magnetic disk unit 20 is fixedly installed on the outer circumference of the hub 33. When the magnetic disk unit 20 has a plurality of magnetic disks, one or more ring-shaped spacers are installed on the outer circumference of the hub 33 to maintain a predetermined distance between the disks. In addition, a clamp 35 is joined to the upper portion of the hub 33 to prevent the magnetic disk unit 20 from being separated from the hub 33.
As described above, the conventional hard disk drive has a structure in which the shaft 32 of the spindle motor 30 is directly joined and fixed to the cover plate 12. As a result, since vibrations generated by the spindle motor 30 are directly transferred to the cover plate 12, and again transferred to the base plate 11 connected to the cover plate 12, there is a problem in which the whole hard disk drive vibrates, and accordingly noises increase.
The vibrations generated by the spindle motor 30 are transferred to the cover plate 12 in the form of vibrations in the axial direction of the shaft 12 and rocking mode vibrations. Although, in order to block such transference of vibrations, there is a method in which the shaft 32 is not joined to the cover plate 12, this results in another problem. That is to say, when the shaft 32 is not joined to the cover plate 12, the rocking mode frequency of the spindle motor 30 becomes lower. Accordingly, since the rocking mode frequency may match a vibration frequency of the spindle motor 30 due to allowable tolerance, assembly tolerance, and the like of a ball bearing of the spindle motor 30, there is a possibility that the resonance phenomenon can severely affect the performance of the hard disk drive. In addition, vibrations generated by the spindle motor 30 result in fluttering of the disk 20 and this also affects the performance of the hard disk drive.
Therefore, in order to ensure the reliability of the performance of a hard disk drive, vibrations generated during the operation of the hard disk drive need to be reduced. Further, since a personal computer employing a hard disk drive must be compatible with relatively quiet surroundings, restraint of vibrations of a hard disk drive, and resultant reduction of noises are increasingly important problems to be solved.